The present invention relates to material classifiers, and more particularly to material classifiers having a scoop wheel.
Material classifiers are used for many different purposes, including the separation or classification of solids according to size and/or particle density. The solids to be separated are mixed in a suitable liquid such as water, to create a liquid-solid mixture or pulp which is then passed to the tank of the classifier. Larger particles settle to the bottom of the classifier tank while fine particles remain in suspension in the liquid medium (called the overflow) which is drawn or overflows from the classifier. Material classifiers also provide cleaning of the solid particles.
Many different types of material classifiers are known, including mechanical and non-mechanical types. One type of mechanical classifier uses a driven wheel having flights, lifts, drags, blades, scoops, scrappers or other means to lift solid material which has settled on the bottom of the tank and discharge it upon a discharge chute, conveyor belt or other means for collecting and transporting the settled material.
A known material classifier, an example of which can be seen in U.S. Pat. No. 1,107,472, issued Aug. 18, 1914, uses V-shaped troughs (“buckets”) or scrapers spaced around the circumference of a cylindrical classifier tank or vessel. The vessel is partially filled with water and slowly rotates. Materials lighter than water will float on the Water's surface and be discharged from the vessel via an overflow trough. Heavier materials sink to the bottom of the vessel and are scooped-up by the buckets as they rotate. When the buckets reach a specified height within the vessel, the contents of the buckets are dumped onto a spout which discharges the material from the vessel.
Another known material classifier, an example of which can be seen in U.S. Pat. No. 2,226,750, issued Dec. 31, 1940, uses a circular wheel with radially spaced blades. Heavier solids scooped-up by the blades are pushed to a discharge lip. Lighter solids are kept in suspension and exit the classifier at an overflow point such as a weir. The classifier blades have a cam mechanism which allows the blades to retract as they move upwards beyond the discharge lip. On the downward rotation the blades are lowered into the water edgewise to minimize the liquid surge caused by the blades entering the water.
Most known sand classifiers and cleaning systems use a screw mechanism for moving the sand along the classifier. These designs are commonly referred to as rotary-drum or screw-conveyor type classifiers, an example of which can be seen in U.S. Pat. No. 4,151,074, issued Apr. 24, 1979. Screw classifiers can be complex, prone to wear, and can be expensive and costly to maintain and set up.
A common drawback of existing classifier designs is that good classifying ability is typically achieved at the expense of capacity and vice versa. Typically, a material classifier has either: (1) good classifying ability but low capacity and a complicated reclaiming system; or (2) high capacity and relatively simple reclaiming system but poor classifying ability. Also, material classifiers with good classifying ability typically offer a much greater classifying ability than is typically required as most finer grade materials have fewer uses.
A further drawback of most material classifiers is that they are large and not easily portable between job sites. Typically, material classifiers must be loaded onto a truck, for example using a forklift, lift truck or crane, transported to the designed location, and then unloaded. Loading and unloading of the classifier results in significant downtime and requires equipment at both the initial and final destinations to perform the loading/unloading operation.
Thus, there is a need for a material classifier that is more cost effective and reliable, less prone to wear and requiring lower maintenance, has a higher capacity and/or that is more compact and can be more easily transported.